1. Field of the Invention
The present invention relates to a DCDC converter, and a semiconductor device and a power generation device including a DCDC converter.
2. Description of the Related Art
A DCDC converter is a constant-voltage circuit with which a constant output voltage can be obtained regardless of the value of input voltage, and the DCDC converter is used for a power supply circuit together with a rectification circuit or the like. In particular, a power supply circuit including a switching-type DCDC converter is referred to as a switching power source or a switching regulator.
The switching-type DCDC converter outputs voltage of a desired level in such a manner that voltage with a pulse waveform is formed using input voltage by a switching element and the voltage is smoothed or held in a coil, a capacitor, or the like. With a switching-type DCDC converter, internal power loss can be small theorically, whereby power conversion efficiency can be high and heat radiation due to power loss can be suppressed in comparison with a linear-type DCDC converter utilizing voltage drop due to resistance.
In Patent Document 1 below, a solar power storage device is disclosed in which voltage generated by a solar cell is converted to charging voltage in accordance with a driving clock by a voltage conversion circuit and a duty ratio of the driving clock is determined in accordance with the maximum charging power which is determined by the above generated voltage. In addition, in Patent Document 2 below, a power supply control device is disclosed in which a voltage difference between a source and a drain of a FET serving as a switching element is monitored and the FET is turned on when the voltage difference exceeds a threshold value, so that it is capable of dealing with a sudden increase of the amount of power consumption in a load.